Diff for "Subrepository"

Subrepositories

This feature is considered experimental for Mercurial 1.3 and is subject to change

Subrepositories is a feature that allows you to treat a collection of repositories as a group. This will allow you to clone, commit to, push, and pull projects and their associated libraries as a group.

1. Basic Usage

1.1. Start

To start using subrepositories, you need two repositories, a main repo and a nested repo:

$ hg init main
$ cd main
$ hg init nested
$ echo test > nested/foo
$ hg -R nested add nested/foo

Now we'll mark nested as a subrepository by creating an entry for it in the special .hgsub file. The first 'nested' is the path in our working dir, and the second is a URL or path to pull from. Here we're simply going to pull from 'nested' using a path relative to main. This says 'anyone who can find our main repo can find the nested repo just by tacking nested onto that path'.

$ echo nested = nested > .hgsub
$ hg add .hgsub

1.2. Committing

When we commit, Mercurial will attempt to recursively commit in all defined subrepos and then record their resulting states in a special .hgsubstate file:

$ hg ci -mtest
committing subrepository nested
$ cat .hgsubstate
3f68b2f93426b6966b604536037b5d325ba00741 nested

At this point of our example, we have the following directory structure:

  main/
      .hg/
      .hgsub
      .hgsubstate
      nested/
          .hg/
          foo

with .hgsub containing

nested = nested

and .hgsubstate containing

3f68b2f93426b6966b604536037b5d325ba00741 nested

Whenever newer Mercurial versions encounter this .hgsubstate file when updating your working directory, they'll attempt to pull the specified subrepos and update them to the appropriate state:

$ cd ..
$ hg clone main main2
updating working directory
pulling subrepo nested
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat main2/nested/foo
test

Subrepos may also contain their own subrepos and Mercurial will recurse as necessary.

2. Caveats

As this is a complex new feature, there are a number of rough edges. Please consider this code to be experimental and expect that some behaviors may change.

Most commands such as diff and status are currently completely unaware of subrepositories. Currently only update, commit, and push are subrepo-aware.

Further, there are a number of behaviors that are currently poorly defined or implemented:

• Update/merge currently can't remove subrepositories entirely as that might lose local-only changes
• There's no support for merging across renaming/moving subrepos
• Collisions between normal files and subrepos are not handled
• Subrepository pulls are always delayed until needed by an update

• Updating always uses the URL from .hgsub (or any default you've specified in the subrepo's hgrc), rather than any you might have specified in your last pull. Pull -r will not filter revisions pulled in subrepositories.

• Push similarly ignores URLs and revision filters
• Commit doesn't propagate some flags like -A to subrepos

3. Internals

The .hgsub format uses the template/hgrc config format. It reserves a source prefix of [ for future expansion (see below). Future expansion may also used named sections in this file.

The .hgsubstate format is similar to the tags format, in the form <revision><space><path>. This file is not intended to be hand-edited, but will accept any identifier format that hg accepts. It is also automatically merged when necessary. It is separated from .hgsub to keep automatic updates from muddling that file and to keep .hgsub's history tidy. The combined state can be viewed with hg debugsub.

Internally, subrepo states are represented as a hash of path to (source, revision) pairs that combine the elements of the above two files. There is also a new subrepo object type that exposes a limited set of operations on a subrepo. Subrepos can be traversed like this:

# check whether subrepos are dirty
c = repo['tip']
for s in c.substates:
    subrepo = c.sub[s]
    print s, subrepo.dirty()

4. To Do

• Add command-line support
• Handle deletion of subrepos more completely
• Reduce spurious message output such as 'nothing changed'
• It should be quite easy to extend this feature to support non-native subrepos from other systems such as git or SVN.